Error using Invoices->update_status($invoiceId) method: Unexpected token 'n', "null" is not valid JSON

[JuanDeLeon]

When calling $facturapi->Invoices->update_status("xxxxxxxxxxxxxxx")
I get the following error:

{#1231 ▼
  +"message": "Unexpected token 'n', "null" is not valid JSON"
  +"status": 400
  +"ok": false
}

I noticed the issue is in Invoices.php class, in the method execute_JSON_put_request it is sending null as the $body parameter.

This is in PHP 8.1, not sure if that's the problem.
Anyway, changing the null for an empty array [] seems to solve the issue.